Wireless cellular communication devices must function well in a variety of propagation environments. For example, in dense urban propagation environments a large number of buildings may block a direct path between a base station and a mobile terminal and cause a number of reflections for the downlink wireless signal arriving at the mobile terminal. In suburban propagation environments, the environment consists of more widely spaced smaller buildings and it is generally easier to obtain a more direct line of sight to a cellular base station, causing fewer wireless signal reflections.
As part of receiver processing, propagation paths are tracked as observed by the receiver. However, new propagation paths may appear, especially in dense urban environments, as a mobile terminal moves. It is beneficial to identify the presence and location of such a new propagation path as quickly as possible, as the new propagation path may cause interference to the downlink signal that is currently being received, until the receiver is able to adjust the appropriate control parameters. Similarly, if a propagation path disappears, it is beneficial to identify this event as quickly as possible, in case the appropriate receiver parameters require adjustment.